Mosses and Lichens 



member of the pouch-fungi group (Gasteromycetes) with an 

 alga (Palmella). 



In the majority of lichens the algae are arranged in definite 

 layers, sometimes as in the gelatinous lichens they are distri- 

 buted through the whole thickness of the thallus. The fungus 

 partner which, with but few exceptions, directs the growth of 

 the lichen, determines whether it shall encrust the surface so 

 that it cannot be removed without injury, or whether it shall 

 form shields and ribbons lightly attached, or corals and fringes 

 fastened at one point. 



Although it is impossible without microscopic examination 

 to determine the exact relations of one lichen to another, much 

 pleasure may be derived from an acquaintance with their external 

 form alone. No plants are more readily preserved and none will 



so satisfactorily respond 

 to one's effort to revive 

 them. Even after they 

 have been dry for years 

 they will become as beau- 

 tiful as ever if placed in a 

 moist atmosphere. One 

 may find them every- 

 where and at all times of 

 the year. Their power of 

 absorbing moisture is tru- 

 ly wonderful. It is stated 

 that if living lichens which 

 have become dry in the 

 air, are left in a place 

 saturated with moisture, 

 they take up 35 per cent, 

 of water in two days and 

 as much as 56 per cent, in 

 six days. Certain lichens 

 after a long continuance 

 of dry weather will absorb 

 one-half their own weight 

 of water in ten minutes and will lose it as quickly when exposed 

 to dry air. It is an interesting experiment to put a mass of 

 Reindeer-lichen in a glass of clear water, and note how quickly 



26 



Sticlima jttliginosa. (Dicks.) Nyl. A section 

 showing (0) the upper cortex, () the under cortex, 

 with (r) rhizoids: (m) Pith layer showing hyphae 

 in side and end views, (g) gonidial zone, with the 

 blue-green alga chroococcus. 



